1. Field
The disclosed embodiments relate to a handover apparatus and a handover method in a wireless communication system, and more particularly, to a method and apparatus for performing fast handover based on media independent handover (MIH) in a wireless communication system.
2. Description of the Related Art
A wireless communication system supports mobility of a terminal by using a handover technology. The handover technology is divided into a media access control (MAC) layer handover technology and a network layer handover technology. The MAC layer handover technology is used when a terminal accesses a network in order to perform handover in a wireless local area network (WLAN) according to Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards or in a wireless metropolitan area network (WMAN) according to IEEE 802.16 standards. If the WLAN provides services to a terminal and the terminal performs MAC layer handover, the terminal obtains information on a serving access point (AP) and neighboring APs by performing a probing process. After the information on the neighboring APs is obtained, the terminal selects an optimal AP by comparing intensities of signals which are received from the neighboring APs, to each other. Then, the terminal and the selected AP mutually perform authentication and association and thus the MAC layer handover is completely performed.
Technologies such as a mobile Internet protocol (IP) technology for performing network layer handover in the wireless communication system have been standardized. Furthermore, a fast handover technology is being researched in order to improve the performance of the mobile IP technology in the wireless communication system. For example, fast handover is performed in the wireless communication system as described below in FIG. 1.
FIG. 1 is a diagram for describing a conventional method of performing fast handover in a wireless communication system. Here, the fast handover may be performed after a layer-2 (L2) (MAC layer) selects a target network 104 to which the fast handover is performed, from among neighboring networks of a terminal 100.
Referring to FIG. 1, if a trigger is created in the L2, the terminal 100 in the wireless communication system determines that handover is required and transmits a target network information request message such as a Router Solicitation for Proxy (RtSolPr) message to a serving network 102 in operation 111. In this case, the trigger includes L2 information on the target network 104 of the terminal 100 and the terminal 100 transmits the target network information request message by including the L2 information into the target network information request message.
When the target network information request message is received, the serving network 102 transmits a target network information response message including information on the target network 104, such as a proxy router advertisement (PrRtAdv) message, to the terminal 100 in operation 113.
The terminal 100 checks the information on the target network 104 from the target network information response message that is received from the serving network 102. Then, the terminal 100 creates a care-of address corresponding to the target network 104 by using the information on the target network 104.
After the care-of address is created, the terminal 100 transmits a fast binding update (FBU) message including the care-of address to the serving network 102 in operation 115.
The serving network 102 checks the care-of address from the FBU message and then transmits a handover initiation (HI) message including the care-of address, to the target network 104 in operation 117.
The target network 104 checks the care-of address from the HI message. Then, the target network 104 performs duplicate address detection (DAD) so as to determine whether the care-of address is usable in operation 119. That is, the target network 104 determines whether the care-of address is not duplicated with an address or another care-of address which is used by another terminal in the target network 104. If the care-of address is usable, that is, if the care-of address is not duplicated with another address, the target network 104 transmits a care-of address authentication message such as a handover acknowledge (HAck) message to the serving network 102 in operation 121. Meanwhile, if the care-of address is not usable, that is, if the care of address is duplicated with another address, the target network 104 creates a new care-of address and transmits a message including the new care-of address, such as the HAck message, to the serving network 102 in operation 121.
In this case, the target network 104 forms a tunnel which corresponds to the care-of address and is connected to the serving network 102.
The serving network 102 checks the HAck message that is received from the target network 104 and transmits a fast binding acknowledgement FBAck message including information on the HAck message, to the terminal 100 in operation 123. Then, the serving network 102 forwards data to be forwarded to the terminal 100, to the target network 104 through the tunnel in operation 125.
When the FBack message is received, the terminal 100 performs L2 (MAC layer) handover in operation 127.
Then, the terminal 100 transmits a fast neighbor advertisement (FNA) message to the target network 104 in order to perform layer-3 (L3) (network layer) handover in operation 129.
When the FNA message is received, the target network 104 forwards the data which is received from the serving network 102 and is temporarily stored, to the terminal 100 in operation 131.
As described above with reference to FIG. 1, in a wireless communication system, MAC layer handover and network layer handover have to be integrally used in order to guarantee mobility of a terminal. In this case, if fast handover is performed in the wireless communication system, a trigger that is created in order to perform handover in an L2 may not be clearly determined. In order to solve such problem, an MIH technology is standardized according to IEEE 802.21 standards.
In this case, the wireless communication system supports handover of the terminal by synchronizing the MAC layer handover and the network layer handover which are independently performed by using the MIH technology. Furthermore, the wireless communication system defines horizontal handover only. Thus, the wireless communication system may not sufficiently use functions provided by the MIH technology.